Part of it is the fact that it's actually two women who pressed
charges relating to two different incidents. Part of it are the
circumstances around the events and the fact that he's being
tried under Swedish law.

Here's a rundown of the facts
from The Guardian, which is one of the original publishers of
the WikiLeaks State Department cables and which follows WikiLeaks
closely:

There are two women who are alleging crimes by Assange,
identified as Ms A and Ms W;

Ms A is "only" alleging molestation, but Ms W is alleging
rape;

Speaking to the Swedish newspaper Aftonbladet, Ms A said: "In
both cases, what started out as voluntary sex subsequently
developed into assault", and described Assange as "a man who has
a twisted attitude to women and a problem with taking 'no' for an
answer."

Assange vehemently denies all charges.

Meanwhile, blogger Jessica Valenti
says the charges are "that Assange held one woman down using
his body weight to sexually assault her and that he raped another
woman while she was sleeping", and adds that "there’s nothing in
Swedish law about “sex by surprise” or broken condoms", linking
to this extract
of Swedish law, in English.

So there you have it, folks. Maybe there's a story about a condom
that broke or did not break, but in any case the Swedish police
is seeking Assange's arrest for very serious crimes, sexual
molestation and possibly rape.

(We would add that we don't see a difference between "sex by
surprise" and rape and that if the telling of the incident --
that Assange's condom broke and he refused to withdraw even
though his partner requested it -- is correct, that is also rape,
by definition, since she stopped consenting to the sex.)